Merge pull request #4765 from metabase/style-guide-and-snapshot-tests

.flowconfig

.reduxrc

.storybook/config.js

.storybook/webpack.config.js

frontend/src/metabase/components/Button.info.js

frontend/src/metabase/components/CheckBox.info.js

frontend/src/metabase/components/StackedCheckBox.info.js

frontend/src/metabase/components/Toggle.info.js

...c/metabase/internal/__snapshots__/components.spec.js.snap

frontend/src/metabase/internal/components.spec.js

frontend/src/metabase/internal/components/ColorsApp.jsx

frontend/src/metabase/internal/components/ComponentsApp.jsx

frontend/src/metabase/internal/components/IconsApp.jsx

frontend/src/metabase/internal/lib/components-node.js

frontend/src/metabase/internal/lib/components-webpack.js

frontend/src/metabase/internal/routes.js

frontend/src/metabase/routes.jsx

frontend/stories/CheckBox.js

frontend/stories/StackedCheckBox.js

frontend/stories/Toggle.js